Field of the Invention
The present invention relates to a stacking device and an image forming apparatus.
Description of the Related Art
Conventionally, there have been widely used electrophotographic image forming apparatuses configured to convey a sheet to an image forming unit to form an image on the sheet. Such image forming apparatuses are provided with a sheet stacking tray serving as a sheet storage device. The sheet stacking tray can store various sizes of sheets in the same tray. To be specific, the sheet stacking tray is provided with a trailing edge regulating device and a width regulating unit in such a manner that their positions can be changed according to the size of the set sheet. The trailing edge regulating device regulates an upstream side of the sheet in a conveyance direction, and the width regulating unit regulates the position of the sheet in a width direction perpendicular to the conveyance direction.
As the various sizes of sheets, sheets having predetermined sizes typically defined by a standard (hereinafter, the sheets are referred to as standard-sized sheets, and the sizes are A4, A3, 8.5×11 inches, and 11×17 inches, for example), and sheets having sizes that do not correspond to the above-described sizes under the standard (hereinafter, the sheets are referred to as non-standard-sized sheets) are widely used in various ways.
For the use of the standard-sized sheets, in order to facilitate operations of the width regulating unit and the trailing edge regulating device performed by a user, some sheet stacking trays are provided with labels or engraved marks in positions corresponding to the sizes of the standard-sized sheets to indicate desired positions of the width regulating unit and the trailing edge regulating device. Further, some sheet stacking trays are configured to indicate that the regulating unit and the regulating device are located in desired positions, by a click or the like provided at the time of operations of the regulating unit and the regulating device.
However, when the standard-sized sheets are used, even if the sheet stacking tray is provided with the configuration for facilitating the operations of the width regulating unit and the trailing edge regulating device performed by the user, the operations may fail to be performed as intended by the user. That is, an operation for adjusting the position of the regulating unit or device to an indication such as the label or the engraved mark by visual observation, and the determination based on the click provided at the time of the operation of the regulating unit or device slightly vary depending on each user. Therefore, there is confirmed a case in which the regulating unit or device unintentionally overruns, and slightly deviates from a desired position to be fixed at the position.
For example, when the trailing edge regulating device is set to a shorter side of the sheets than a desired position, the sheets are compressed by the regulating unit more than necessary, and leading edges and trailing edges of the sheets are in a pressed state. As a result, there is problem that a sheet bundle is not lifted up in a swing lift plate due to friction between the leading edges of the sheets and a wall of a leading edge of the tray, or sheet feeding failure occurs due to a loss of lift pressure.
When the trailing edge regulating device is set to a longer side of the sheet than a desired position, a leading edge position of the sheets on the sheet stacking tray may be changed from a desired position, and therefore, a relative position between the sheets and a feed roller that feeds and conveys the sheets may be changed. As a result, there is a problem that such changes may lead to sheet feeding failure such as non-feeding.
Therefore, for example, as described in Japanese Patent Application No. 2007-223686, removing a positioning configuration of the trailing edge regulating device in a boundary of the standard-sized sheet and the non-standard-sized sheet clarifies a fixed position of the standard-sized sheet. As a result, an ideal position of the trailing edge regulating device to be set when the user uses the standard-sized sheet becomes easily-identifiable.
However, in the configuration described in Japanese Patent Application No. 2007-223686, in the vicinity of the position corresponding to the standard-sized sheet, the trailing edge regulating device may be positioned by neither a positioning mechanism of the standard size nor a positioning mechanism of the non-standard size. Since there is nothing to fix the position of the regulating device in a region where the positioning configuration of the regulating device is removed, when the trailing edge regulating device is used with slight deviation, the position of the regulating device changes during passing of the sheets. As a result, there is a problem that the sheet is obliquely conveyed.